A permanent magnet generator (PMG) is used to convert mechanical energy, usually rotational, to electrical energy. The typical PMG receives mechanical energy from a prime mover. The prime mover may be, for example, a gas turbine engine of an aircraft. The prime mover causes a rotor located within the PMG to spin. Magnetic flux created by permanent magnets located on the rotor cause an emf voltage to be generated in stator windings. The accumulation of the voltage generated at each of these coils is provided as an output voltage to a load.
The output voltage generated by the PMG is dependent, in part, on the speed of the prime mover as well as the overall impedance of the load. That is, a decrease in rotational velocity of the prime mover results in a decreased rotational velocity of the rotor, and a resulting decrease in the output voltage generated by the stator windings. An increase in rotation of the prime mover results in an increase of the output voltage generated by the coils in the stator. Likewise, a decrease in the impedance of the load results in an increase in the output voltage of the PMG, and an increase in the impedance of the load results in a decrease in the output voltage of the PMG.
In many applications, variations in the output voltage of the PMG are not acceptable. However, it is not always possible to precisely control the speed of the prime mover or the impedance of the load. In these applications, it would be desirable to be able to maintain the output voltage of the PMG despite variations in speed of the prime mover or impedance of the load. In other applications, it is desirable to be able to control the output voltage of the PMG without having to modify the speed of the prime mover or the impedance of the load.